The present invention relates to a method for producing an avocado leaf plant extract rich in furanic lipids.
Avocado comprises, in a known manner, particular lipids of the furan type, whose main component is a linoleic furan: 
Thus, the expression xe2x80x9cavocado furanic lipidsxe2x80x9d is understood to mean according to the invention the components corresponding to the formula: 
in which R is a linear C11-C19, preferably C13-C17, hydrocarbon chain which is saturated or which comprises one or more ethylenic or acetylenic unsaturations. These avocado furanic lipids have been described in particular in Farines, M et al, 1995, J. of Am. Oil Chem. Soc. 72, 473.
Currently, the known routes of synthesis for producing furanic lipids and the routes commonly used starting from avocados in the form of fruits as raw material.
Given the therapeutic value of avocado furanic lipids for their beneficial and curative action on the connective tissue, in particular in inflammatory pathologies such as osteoarthritis, periodontitis and scleroderma, and their high cost in general, a strong interest therefore exists in finding alternative routes for preparing these avocado furanic lipids.
The Applicant has thus developed a method which makes it possible to obtain an avocado leaf plant extract rich in furanic lipids, namely having a content ranging from 20 to 80%, and preferably 30 to 50%.
This method, in which the raw material consists of avocado leaves, comprises the following steps:
a liquid-solid extraction step followed by evaporation under vacuum, and
a heat treatment step between 80 and 120xc2x0 C.
These two steps may be carried out in this order or in the reverse order.
The avocado leaves may be obtained from avocado plants belonging to the following varieties: Hass, Fuerte, Ettinger, Bacon, Nabal, Anaheim, Lula, Reed, Zutano, Queen, Criola Selva, Mexicana Canta, Region Dschang, Hall, Booth, Peterson, Collinson Red or Alpha Krome and more particularly to the varieties Hass, Fuerte and Reed.
Several solvents may be used during the step of liquid-solid extraction of the leaves, having previously been optionally subjected to dehydration. The solvents may be chosen from the group consisting of alkanes, halogenated alkanes, ethers, esters, alcohols, aromatic compounds and supercritical fluids. Hexane, ethanol, methanol, chloroform, dichloromethane and ethyl acetate are preferred, alone or in the form of a mixture.
The heat treatment step, whether it takes place directly on the leaves or at the plant extract stage, is carried out at temperatures of between 80 and 120xc2x0 C. This heat treatment may last from 5 to 72 hours.
According to the method of the invention, the heat treatment step may be performed in the presence or otherwise of an acid catalyst.
The expression acid catalysts is understood to mean in a broad sense so-called homogeneous inorganic or organic catalysts such as hydrochloric, sulphuric, acetic or para-toluenesulphonic acids, but also, and preferably, heterogeneous solid catalysts such as silica, alumina, silicas-aluminas, zirconias, zeolites and acidic resins. Acidic aluminas with large specific surface areas, that is to say at least equal to 200 m2/g, will be chosen in particular.
The method may also comprise a step, prior to the liquid-solid extraction, of dehydration of avocado leaves.
The expression dehydration of the avocado leaves is understood to mean more generally all the techniques known to persons skilled in the art which make it possible to extract water from a compound. Among these techniques, there may be mentioned drying under a hot air stream or under a controlled atmosphere (e.g. nitrogen) at atmospheric pressure or under vacuum, in a thick layer or in a thin layer, but also microwave drying, spray-drying, freeze-drying and osmotic dehydration in solution (direct osmosis) or in solid phase (e.g. drying in osmotic bags).
In general, the temperature during this dehydration step will be preferably maintained, whatever the technique used, at less than or equal to 80xc2x0 C.
Moreover, it is preferable, in the context of the present invention, to stop the dehydration when the residual moisture reaches the level of 5%.
In the context of the present invention, for the sake of ease of industrial implementation and for cost considerations, drying in ventilated dryers, in a thin layer and under a hot air stream, at a temperature of between 70 and 75xc2x0 C. is preferred. The duration of the operation may vary from 5 to 72 hours.
According to a first variant, the method is carried out according to the succession of steps below:
Step 1: heat treatment of the avocado leaves,
Step 2: liquid-solid extraction of the avocado leaves,
Step 3: vacuum evaporation of the solvent until a solvent-free plant extract is obtained.
According to a second variant, the method is carried out according to the succession of steps below:
Step 1: liquid-solid extraction of the avocado leaves,
Step 2: vacuum evaporation of the solvent until a solvent-free plant extract is obtained,
Step 3: heat treatment of the plant extract.
According to final variant, the method is carried out according to the succession of steps below:
Step 1: dehydration of the avocado leaves,
Step 2: liquid-solid extraction of the avocado leaves,
Step 3: vacuum evaporation of the solvent until a plant extract is obtained,
Step 4: heat treatment of the plant extract.
The leaves are advantageously ground before any operation performed in the context of the method according to the invention.
The present invention finally relates to an avocado leaf plant extract which can be obtained by the method according to the invention, including according to all its variants.